Ideally it would be switched to the head unit by default and switch to tablet when it detects sound from the tablet, that way NAV would happily interrupt the head unit. If I can find this setup I think I'd definitely buy one, otherwise it's just going to feel like 2 separate systems having to switch between them. Maybe I can do without sound from the tablet, not really going to be using it for anything, onboard speakers may suffice for NAV too.

Has anybody determined if indeed the Scosche unit gives priority to the incoming BT audio? Seeems like a sensible thing but did Scosche think of it.

Hey guys, just wanted to update you on my progress. I was able to find a unit similar to the scoche. This unit is made by SONY and uses an app called App Remote. I can confirm that this head unit can establish 2 bluetooth connections very easily. One to the tablet using the media connection and another to the phone using the phone connection. You can see how it works in the video below. For details on the setup you can see the link in my signature to the build.

Head unit is a Sony MEX-BT4100P. They make a cheaper version of this head unit that also utilizes the app remote called the Sony MEX-BT3100P. I'll try to mess with navigation today a bit and see what my results are. Any other questions you have about the app/setup feel free to ask.

They make a cheaper version of this head unit that also utilizes the app remote called the Sony MEX-BT3100P.

I see that. Seems the difference may be the customizable lighting color, and the available pre-outs. I figure I'll use the built-in amp for the car speakers, but use the sub pre-out to my sub/amp. If it works that way.